1. Field of the Invention
The present invention relates to a communication apparatus and method for transmitting and receiving various texts, and more particularly, to those used in a Point of Sales (POS) system and the like.
2. Description of the Related Art
In a large-scale retail store such as a supermarket, a POS system is used to enhance operational efficiency. A typical POS system comprises a single host computer and a plurality of terminals connected to the host computer by a communication cable. The host computer includes a Price Look Up (PLU) file, a sales file, and other files. Article data such as article codes, department codes, unit prices, and other data items of various articles are registered in the PLU file, and sales data such as article codes, sales amounts, and other data items of articles being sold are registered in the sales file. The article data are retrieved from the PLU file and supplied to the terminals via the communication cable. The terminals are, for example, an Electronic Cash Register (ECR) and an Electronic Weighing and Pricing Device (EWPD). The ECRs perform settlement processings on the basis of the article data supplied from the host computer. The EWPDs perform label issuing processings also on the basis of the article data supplied from the host computer. Sales data or the results of the processings are supplied from the terminals to the host computer via the communication cable.
In actual communication, various control texts are required for communication procedures in addition to data texts such as the article data and the sales data. The control and data texts are selectively retrieved as a transmission text, and converted into the form of a character or a series of characters, and supplied to the communication cable. The last character of the transmission text is one of specified control characters and a character of error check data. The specified control character is provided for the control text, and the character of error check data is provided for the data text. The error check data is used in horizontal parity check or the like effected to detect a reception error.
Recently, there appeared a POS system in which the host computer communicates with terminals by means of radio communication units respectively connecting the terminals to the host computer. Each radio communication unit stores a transmission text formed of one or more characters sequentially supplied from the host computer or the terminal, and performs a transmission process on the transmission text. Completion of preparing the transmission text is confirmed when the character supply has been stopped for a predetermined amount of time. In the transmission process, the stored characters are converted to a radio signal and transmitted from the radio communication unit.
However, time is being wasted while the predetermined amount of time elapse before the preparation of transmission text is confirmed. In other words, the transmission process cannot be started immediately after the last character of the transmission text have been provided.